JP7196697B2 - toner - Google Patents

Description

The present invention relates to toner.

In image formation by electrophotography, a toner containing toner particles having toner base particles is used. The toner base particles include, for example, a toner core containing a binder resin and magnetic powder, and a shell layer covering the surface of the toner core (Patent Documents 1 and 2).

JP 2009-98257 A JP-A-62-099763

However, with the toner using the toner base particles described in Patent Documents 1 and 2, the toner layer (toner chain) formed on the developing roller has a wide charge amount distribution, so it is difficult to obtain sufficient image density. This has been made clear by the inventor's studies.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a toner in which a toner chain formed on a developing roller has a narrow charge amount distribution and, as a result, excellent image density. .

The toner of the present invention comprises toner particles having toner base particles. The toner base particles include a toner core and a shell layer covering the surface of the toner core. The toner core contains a first binder resin and magnetic powder. The shell layer contains a second binder resin, an azine compound and strontium titanate particles.

The toner of the present invention has a narrow charge amount distribution of the toner chain formed on the developing roller, and is excellent in image density.

1 is a schematic cross-sectional view showing an example of toner according to an embodiment of the invention; FIG. FIG. 4 is a diagram showing an outline of a cole-cole plot; It is a cole-cole plot of toners (T-1) to (T-5). It is a cole-cole plot of toners (T-6) to (T-7) and (t-1) to (t-3). It is a cole-cole plot of toners (t-4) to (t-7). 4 is an enlarged view near the origin of the cole-cole plot of FIG. 3; FIG. 5 is an enlarged view near the origin of the cole-cole plot of FIG. 4; FIG. 6 is an enlarged view near the origin of the cole-cole plot of FIG. 5. FIG.

Preferred embodiments of the present invention are described below. Note that the toner is an aggregate (for example, powder) of toner particles. The external additive is an aggregate (for example, powder) of external additive particles. Evaluation results (values indicating shape, physical properties, etc.) regarding powder (more specifically, powder of toner particles, powder of external additive particles, etc.) are the It is the number average of the values measured for each of the selected particles.

The measured value of the volume median diameter (D ₅₀ ) of the powder was measured using a laser diffraction/scattering particle size distribution analyzer ("LA-950" manufactured by Horiba, Ltd.) unless otherwise specified. is the median diameter.

Unless otherwise specified, the number average primary particle diameter of the powder is the circle-equivalent diameter of the primary particles measured using a scanning electron microscope (Heywood diameter: a circle having the same area as the projected area of the primary particles diameter). The number average primary particle diameter of the powder is, for example, the number average value of equivalent circle diameters of 100 primary particles. The number average primary particle size of particles refers to the number average primary particle size of particles in powder unless otherwise specified.

Chargeability means chargeability in triboelectrification unless otherwise specified. The strength of positive chargeability (or the strength of negative chargeability) in triboelectrification can be confirmed by a known electrification series or the like.

The softening point (Tm) is a value measured using a Koka flow tester ("CFT-500D" manufactured by Shimadzu Corporation) unless otherwise specified. In the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured with a Koka flow tester, the temperature at which "(baseline stroke value + maximum stroke value) / 2" is Tm (softening point) Equivalent to.

The glass transition point (Tg) is a value measured according to "JIS (Japanese Industrial Standards) K7121-2012" using a differential scanning calorimeter ("DSC-6220" manufactured by Seiko Instruments Inc.) unless otherwise specified. is. In the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) measured with a differential scanning calorimeter, the temperature at the inflection point caused by the glass transition (specifically, the extrapolated line of the baseline and the falling edge The temperature at the intersection of the line with the extrapolated line) corresponds to Tg (glass transition point).

The acid value of the polyester resin can be measured by a method conforming to JIS (Japanese Industrial Standards) K0070-1992.

Resin molecular weights (eg, number average molecular weight (Mn) or weight average molecular weight (Mw)) are measured using gel permeation chromatography unless otherwise specified.

A "major component" of a material means, by mass, the component that is the most abundant in the material, unless otherwise specified.

The strength of hydrophobicity (or the strength of hydrophilicity) can be represented, for example, by the contact angle of a water droplet (easiness of wetting with water). The greater the contact angle of water droplets, the stronger the hydrophobicity.

Hereinafter, compounds and derivatives thereof may be collectively referred to by adding "system" to the name of the compound. When the polymer name is expressed by adding "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

<Toner>
Toners according to embodiments of the present invention comprise toner particles comprising toner base particles. The toner base particles have a toner core and a shell layer covering the surface of the toner core. The toner core contains a first binder resin and magnetic powder. The shell layer contains a second binder resin, an azine compound and strontium titanate particles.

The toner of the present invention can be suitably used for developing electrostatic latent images, for example, as a positively charged magnetic toner (single-component developer).

FIG. 1 shows an example of toner particles 1 contained in the toner of the present invention. The toner particles 1 shown in FIG. The toner base particles 2 have a toner core 2a and a shell layer 2b covering the surface of the toner core 2a. However, the toner particles contained in the toner of the present invention may have a structure different from that of the toner particles 1 shown in FIG. For example, the toner particles may be free of external additives. The toner of the present invention has been described above with reference to FIG.

Since the toner of the present invention has the above-described structure, the toner chain formed on the developing roller has a narrow charge amount distribution and is excellent in image density. The reason is explained below. When the toner of the present invention is used as a one-component developer, the toner particles form a thin toner layer (toner chain) supported by magnetic binding force on the developing roller. The toner particles in the toner chains are charged by charges generated by triboelectrification with the developer roller surface. Specifically, the toner particles in the toner chain are first charged by the toner particles existing on the developing roller side due to triboelectrification with the developing roller. All toner particles in the toner chain are then charged by sequential transfer of charge from a charged toner particle on the side of the developer roller to an adjacent toner particle. From the viewpoint of obtaining an appropriate image density, the magnetic toner is required to promote charge transfer between the developing roller and the toner particles, and charge transfer between the toner particles, and evenly charge the toner particles in the toner chain. be done.

The toner of the present invention has a shell layer containing an azine compound. The azine compound has a low work function and functions to reduce the grain boundary time constant of the toner particles. Therefore, the toner particles can efficiently transfer charge through their surface (the surface of the shell layer). In addition, since the shell layer of the toner particles contains strontium titanate capable of retaining a relatively large amount of electric charge, the above-described electric charge transfer is promoted. As a result, in the toner chains formed by the toner of the present invention, all the toner particles tend to be evenly charged. Therefore, the toner of the present invention has a narrow charge amount distribution of the toner chain formed on the developing roller, and is excellent in image density.

Here, the electrical properties of the toner particles in the toner chain will be described. Considering the resistance component R and the capacitance component C as electrical characteristics, the toner particles can be regarded as an RC parallel electrical circuit. Therefore, the resistance component R and the capacitance component C can be calculated by pelletizing the toner particles and then measuring the complex impedance. The time constant that determines the charging speed of the sample (pelletized toner particles) is obtained by calculating "resistance component R×capacitance component C (or resistivity ρ×dielectric constant ε considering sample conditions)=τ". can ask.

Here, in complex impedance measurement, the relationship between the measured resistance component R and reactance X is represented by a "cole-cole plot." A cole-cole plot yields a capacitive semicircle depending on the electrical response of the sample from high frequencies to low frequencies. The capacitive semicircle shows the electrical response of the sample as a function of frequency. In measurements using pelletized toner particles as a sample, the capacitive semicircle usually indicates an electrical response originating from the internal components of the toner particles.

As exemplified in FIG. 2, in the cole-cole plot, the capacitive semicircle (hereinafter sometimes referred to as the capacitive semicircle R _{H CH} ) showing the electrical response originating from the components inside the toner particle In some cases, a capacitive semicircle (hereinafter sometimes referred to as a capacitive semicircle R _{L CL} ) that exhibits an electrical response originating from the interface of the toner particles is obtained. The capacitive semicircle R _{L CL} is obtained in the lower frequency region of the cole-cole plot (the right region in FIG. 2) compared to the capacitive semicircle R _{H CH} . The time constant τ _L [sec], which is the product of the resistivity ρ _L [Ωm] calculated from the capacitive semicircle R _L C _L and the dielectric constant ε _L [F/m], and the capacitive semicircle R _H C When the time constant τH [sec], which is the product of the resistivity _ρH [Ωm] calculated from _H and the dielectric constant _εH [ _F /m], differs by a factor of about 100 or more, the capacitive semicircle R The _LCL and capacitive _{semicircles RHCH become} distinguishable.

The electrical response originating from the toner particle interface corresponds to electron migration at the surface of the toner particles within the toner chain. Therefore, in the measurement frequency range, when an electrical response originating from the toner particle interface is observed (when a capacitive semicircle R _L C _L is obtained), the time constant of the sample is small and the electron transfer in the toner chain is means faster.

As described above, the toner of the present invention has a capacitive semicircle that can be separated into a high frequency region and a low frequency region when the complex impedance is measured in a pelletized state between the powder electrodes and a cole-cole plot is formed. It is preferred to have Further, the toner of the present invention has a resistivity ρ _L [Ωm], a dielectric constant ε _L [F/m], and a The relationship between the product of the time constant τ _L [seconds], the resistivity ρ _H [Ωm], the dielectric constant ε _H [F/m], and the product of the time constant τ _H [seconds] is given by the following relational expression: It is more preferable to satisfy (1) to (3). The complex impedance shall be measured by the same method as the measuring method described in the examples.
τ _H (=ρ _H ×ε _H )<1 [second] (1)
50×τ _H <τ _L (2)
ρ _L <1×10 ¹¹ [Ωm] (3)

Here, in the relational expression (1), when τ _H >1 [second], the charging speed of the toner chain formed on the developing roller by the toner becomes slow, and the tendency that the charge amount distribution of the toner chain is difficult to become narrow. There is

In relational expression (2), when 50×τ _H ≧τ _L (that is, when there is only one capacitive semicircle, or when the capacitive semicircle cannot be clearly divided into two), the toner particles Electron transfer at the interface tends to be difficult. Therefore, the charging speed in the toner chain formed on the developing roller by the toner is slowed down, and the charge amount distribution of the toner chain tends to be difficult to become narrow.

Since the charging speed between the developing roller and the toner particles is affected by the resistivity of both, a lower _ρL is preferable. In relational expression (3), when ρ _L >1×10 ¹¹ [Ωm], the charging speed of the toner particles on the developing roller side of the toner chain becomes insufficient, and the charge amount distribution of the toner chain tends not to become narrow. be.

[Toner base particles]
The toner base particles have a toner core and a shell layer covering the surface of the toner core. From the viewpoint of forming good images, the volume median diameter (D ₅₀ ) of the toner base particles is preferably 4 μm or more and 9 μm or less.

(toner core)
The toner core contains a first binder resin and magnetic powder. The toner core may further contain an internal additive (eg, at least one of a colorant, release agent, and charge control agent), if desired. Methods for producing toner cores include a pulverization method and an agglomeration method, with the pulverization method being preferred.

(First binding resin)
The toner core contains, for example, a first binder resin as a main component. From the viewpoint of providing a toner excellent in low-temperature fixability, the toner core preferably contains a thermoplastic resin as the first binder resin, and the thermoplastic resin accounts for 85% by mass or more of the entire first binder resin. Containing is more preferable. Examples of thermoplastic resins include styrene-based resins, acrylic acid ester-based resins, olefin-based resins (more specifically, polyethylene resins, polypropylene resins, etc.), vinyl resins (more specifically, vinyl chloride resins, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, etc.), polyester resin, polyamide resin, and urethane resin. In addition, copolymers of these resins, that is, copolymers in which arbitrary repeating units are introduced into the above resins (more specifically, styrene-acrylic acid ester-based resins, styrene-butadiene-based resins, etc.) It can be used as the first binder resin. As the first binder resin, a polyester resin is preferable, and an amorphous polyester resin is more preferable.

The content of the first binder resin in the toner core is preferably 30% by mass or more and 90% by mass or less, more preferably 40% by mass or more and 70% by mass or less.

A polyester resin is obtained by condensation polymerization of one or more polyhydric alcohols and one or more polycarboxylic acids. Examples of polyhydric alcohols for synthesizing polyester resins include dihydric alcohols (more specifically, diols, bisphenols, etc.) and trihydric or higher alcohols, as shown below. Examples of polyvalent carboxylic acids for synthesizing polyester resins include divalent carboxylic acids and trivalent or higher carboxylic acids as shown below. Instead of the polycarboxylic acid, a polycarboxylic acid derivative capable of forming an ester bond by polycondensation (for example, an anhydride of polycarboxylic acid, a polycarboxylic acid halide, etc.) may be used.

Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 2-butene-1,4-diol. , α,ω-straight-chain alkanediols having 5 to 30 carbon atoms (more specifically, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,23-trico 2-pentene-1,5-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, 1,4-benzenediol, polyethylene glycol, polypropylene glycol, and poly Tetramethylene glycol is mentioned.

Bisphenols include, for example, bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

Examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxy Methylbenzene can be mentioned.

Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, and those having 10 to 35 carbon atoms. of α,ω-straight-chain alkanedicarboxylic acids (more specifically, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,26-hexa cosane dicarboxylic acid, 1,28-octacosane dicarboxylic acid, etc.), malonic acid, succinic acid, alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid) acid, isododecyl succinic acid, etc.), and alkenyl succinic acid (more specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, isododecenyl succinic acid, etc.) mentioned.

Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2, 4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxylpropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid.

The physical properties of the polyester resin suitable for the first binder resin are described below. The number average molecular weight (Mn) of the polyester resin is preferably 1,000 or more and 5,000 or less, more preferably 1,200 or more and 1,800 or less. The mass average molecular weight (Mw) of the polyester resin is preferably 250 or more and 5,000 or less, more preferably 300 or more and 350 or less. The acid value of the polyester resin is preferably 10 mgKOH/g or more and 50 mgKOH/g or less, more preferably 20 mgKOH/g or more and 25 mgKOH/g or less. The softening point (Tm) of the polyester resin is preferably 50° C. or higher and 90° C. or lower, more preferably 65° C. or higher and 80° C. or lower. The glass transition point (Tg) of the polyester resin is preferably 40° C. or higher and 70° C. or lower, more preferably 50° C. or higher and 60° C. or lower.

(Magnetic powder)
Materials for the magnetic powder include, for example, ferromagnetic metals (more specifically, iron, cobalt, nickel, alloys containing one or more of these metals, etc.), ferromagnetic metal oxides (more specifically, (ferrite, magnetite, chromium dioxide, etc.) and ferromagnetization-treated materials (more specifically, carbon materials to which ferromagnetism is imparted by heat treatment, etc.) can be preferably used.

From the viewpoint of forming a good image, the content of the magnetic powder in the toner core is preferably 40 parts by mass or more and 120 parts by mass or less, and 50 parts by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the first binder resin. is more preferred.

The number average primary particle size of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.3 μm or less.

In order to suppress the elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. When the metal ions are eluted on the surface of the toner particles, the toner particles are likely to adhere to each other. It is believed that by suppressing the elution of metal ions from the magnetic powder, it is possible to suppress the sticking of the toner particles to each other.

(coloring agent)
The toner core may contain colorants. As the colorant, a known pigment or dye can be used according to the color of the toner. From the viewpoint of forming a high-quality image using the toner, the content of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the first binder resin.

The toner core may contain a black colorant. Examples of black colorants include carbon black. The black colorant may be magnetic powder. That is, the toner core may contain no colorant other than the magnetic powder.

(Release agent)
The toner core may contain a release agent. A release agent is used, for example, for the purpose of imparting anti-offset properties to the toner.

Release agents include, for example, aliphatic hydrocarbon waxes (e.g., low-molecular-weight polyethylene, low-molecular-weight polypropylene, polyolefin copolymers, polyolefin waxes, microcrystalline waxes, paraffin waxes, and Fischer-Tropsch waxes), aliphatic hydrocarbons, oxides of waxes (e.g., oxidized polyethylene waxes and block copolymers of oxidized polyethylene waxes), vegetable waxes (candelilla wax, carnauba wax, Japan wax, jojoba wax, and rice wax), animal waxes (e.g., , beeswax, lanolin, and spermaceti), mineral waxes (e.g., ozokerite, ceresin, and petrolatum), ester waxes based on fatty acid esters (e.g., montanate wax and castor wax), and fatty acid ester waxes Partially or wholly deoxidized waxes (eg, deoxidized carnauba wax) are included. Carnauba wax is preferred as the release agent.

From the viewpoint of imparting sufficient offset resistance to the toner, the content of the release agent is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the first binder resin.

When the toner core contains a release agent, the compatibility agent may be further added to the toner core in order to improve compatibility between the first binder resin and the release agent.

(Charge control agent)
The toner core may contain charge control agents. Charge control agents are used, for example, to provide toners with better charge stability or better charge rise characteristics. The charging rise characteristic of the toner is an index of whether or not the toner can be charged to a predetermined charging level in a short period of time.

(shell layer)
The shell layer contains a second binder resin, an azine compound and strontium titanate particles. The mass of the shell layer in the toner base particles is preferably 10 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the toner core.

(Second binder resin)
As the second binder resin, for example, resins similar to the resins exemplified for the first binder resin can be used. The second binder resin is preferably a thermoplastic resin, more preferably a polyester resin, and more preferably an amorphous polyester resin, from the viewpoint of low-temperature fixability of the toner.

The physical properties of the polyester resin suitable for the second binder resin are described below. The number average molecular weight (Mn) of the polyester resin is preferably 1,000 or more and 5,000 or less, more preferably 1,500 or more and 2,500 or less. The mass average molecular weight (Mw) of the polyester resin is preferably 300 or more and 800 or less, more preferably 400 or more and 500 or less. The acid value of the polyester resin is preferably 5 mgKOH/g or more and 30 mgKOH/g or less, more preferably 10 mgKOH/g or more and 20 mgKOH/g or less. The softening point (Tm) of the polyester resin is preferably 60° C. or higher and 100° C. or lower, more preferably 70° C. or higher and 90° C. or lower. The glass transition point (Tg) of the polyester resin is preferably 40° C. or higher and 80° C. or lower, more preferably 50° C. or higher and 65° C. or lower.

The content of the second binder resin in the shell layer is preferably 20% by mass or more and 75% by mass or less, more preferably 30% by mass or more and 60% by mass or less.

(Azine compound)
An azine compound is a compound having a skeleton structure (azine skeleton) represented by the following formula. In the formula below, X represents a nitrogen atom, an oxygen atom or a sulfur atom. X is preferably a nitrogen atom.

Examples of azine compounds include "BONTRON (registered trademark) N-71", "BONTRON N-75", "BONTRON N-77", "N-79", "N-100" manufactured by Orient Chemical Industry Co., Ltd. can be used.

The content of the azine compound in the shell layer is preferably 15 parts by mass or more and 150 parts by mass or less, more preferably 35 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the second binder resin. By setting the content of the azine compound in the shell layer to 15 parts by mass or more and 150 parts by mass or less, the charging speed of the toner chains formed on the developing roller by the toner tends to increase.

(Strontium titanate particles)
Strontium titanate particles are particles containing strontium titanate (SrTiO ₃ ) as a main component. The content of strontium titanate in the strontium titanate particles is preferably 80% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass. The number average primary particle diameter of the strontium titanate particles is preferably 30 nm or more and 300 nm or less, more preferably 50 nm or more and 100 nm or less.

The content of the strontium titanate particles in the shell layer is preferably 30 parts by mass or more and 200 parts by mass or less, more preferably 70 parts by mass or more and 120 parts by mass or less with respect to 100 parts by mass of the second binder resin. By setting the content of the strontium titanate particles in the shell layer to 30 parts by mass or more and 200 parts by mass or less, the charging speed of the toner chains formed on the developing roller by the toner tends to increase.

[External Additive]
The toner particles preferably have an external additive adhering to the surface of the toner base particles. The external additive includes external additive particles. Inorganic particles are preferable as the external additive particles. Examples of inorganic particles include silica particles (especially dry silica particles), and particles of metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate). is mentioned. Silica particles are preferred as the inorganic particles. The number average primary particle diameter of the inorganic particles is preferably 1 nm or more and 100 nm or less, more preferably 5 nm or more and 40 nm or less.

When the toner particles are provided with an external additive, the content thereof is preferably 0.01 parts by mass or more and 10 parts by mass or less, and 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner base particles. more preferred.

<Toner manufacturing method>
The toner of the present invention can be produced, for example, by a production method comprising a toner core preparation step of preparing a toner core and a shell layer forming step of obtaining toner base particles by forming a shell layer covering the surface of the toner core. . The manufacturing method described above may further include an external addition step of attaching an external additive to the surface of the toner base particles, if necessary.

[Toner core preparation process]
In this step, a toner core is prepared. A method for producing the toner core is not particularly limited, and a known pulverization method and a known agglomeration method can be used. A pulverization method is preferable as the method for producing the toner core.

[Shell Layer Forming Step]
In this step, a shell layer covering the surface of the toner core is formed. As a method for forming the shell layer, for example, particles containing a second binder resin, an azine compound, and strontium titanate particles (hereinafter sometimes referred to as shell layer material) and toner cores are mixed in an aqueous dispersion. A method of reacting with

The shell layer material can be obtained by melt-kneading the second binder resin, the azine compound, and the strontium titanate particles, and then pulverizing the kneaded product. Examples of the method of pulverizing the kneaded material include a method of pulverizing the kneaded material with a known screen-type medium crusher, fine pulverizer, or the like, and then further pulverizing the obtained pulverized material with a bead mill or the like. Pulverization with a bead mill is preferably carried out in an aqueous medium containing a surfactant (eg, sodium lauryl sulfate, etc.) and triethanolamine, etc.

The reaction conditions for reacting the shell layer material and the toner core in the aqueous dispersion include, for example, a reaction temperature of 50° C. to 90° C., a reaction time of 30 minutes to 5 hours, and a pH of 3 to 5. . The obtained toner base particles may be washed and dried as necessary.

[External addition process]
In this step, an external additive is adhered to the surface of the toner base particles. As a result, toner particles comprising the toner base particles and the external additive adhering to the surfaces of the toner base particles are obtained. The method of adhering the external additive to the surface of the toner base particles is not particularly limited, but an example thereof includes a method of stirring the toner base particles and the external additive with a mixer or the like.

EXAMPLES Hereinafter, the present invention will be described more specifically using examples. However, the present invention is in no way limited to the scope of the examples.

<Toner manufacturing>
Toners of Examples and Comparative Examples were produced by the following method. First, the materials used to manufacture each toner will be described.

(Additive)
Additive (N-71): azine compound, "BONTRON (registered trademark) N-71" manufactured by Orient Chemical Industry Co., Ltd.
Additive (N-77): azine compound, "BONTRON (registered trademark) N-77" manufactured by Orient Chemical Industry Co., Ltd.
Additive (N-79): azine compound, "BONTRON (registered trademark) N-79" manufactured by Orient Chemical Industry Co., Ltd.
Additive (N-100): azine compound, "BONTRON (registered trademark) N-100" manufactured by Orient Chemical Industry Co., Ltd.
Additive (P-51): quaternary ammonium salt, Orient Chemical Industry Co., Ltd. "BONTRON (registered trademark) P-51"

(Inorganic particles)
Inorganic particles (SW-350): "SW-350" manufactured by Titan Kogyo Co., Ltd., number average primary particle diameter 80 nm
Inorganic particles (KA-30): "KA-30" manufactured by Titan Kogyo Co., Ltd., number average primary particle diameter 300 nm
Inorganic particles (KA-20): "KA-20" manufactured by Titan Kogyo Co., Ltd., number average primary particle size 355 nm

(Binder resin)
Polyester resin 1: "Polyester resin KDC-65" manufactured by Kao Corporation, Mn 1,429, Mw 312, acid value 22.5 mg KOH / g, Tm 72.3 ° C., Tg 53.1 ° C.
Polyester resin 2: "Polyester resin KMCH-4" manufactured by Kao Corporation, Mn 1,882, Mw 432, acid value 13.4 mg KOH / g, Tm 80.1 ° C., Tg 57.1 ° C.

(Preparation of toner core A)
In an FM mixer ("FM-20B" manufactured by Nippon Coke Kogyo Co., Ltd.), 2,240 g of a first binder resin (polyester resin 1) and magnetic powder ("Magnetite MRO-15A" manufactured by Toda Kogyo Co., Ltd.) were added as toner core materials. , number average primary particle size 0.18 μm) and 160 g of carnauba wax (Kato Yoko Co., Ltd. “Special Carnauba No. 1”) as a release agent were added. The contents of the FM mixer were then mixed at a rotation speed of 2,000 rpm for 5 minutes. As a result, a toner core material mixture containing the first binder resin (100 parts by mass), the magnetic powder (71.4 parts by mass) and the release agent (7.1 parts by mass) was obtained.

The mixture of the obtained toner core materials was extruded using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) at a material feed rate of 6 kg/hour, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 100°C. It was melt-kneaded under the following conditions. The resulting melt-kneaded product was cooled. The cooled melt-kneaded product was coarsely pulverized using a pulverizer ("Rotoplex (registered trademark)" manufactured by Hosokawa Micron Corporation) under the condition of a set particle size of 2 mm or less. The obtained coarsely pulverized material was finely pulverized using a pulverizer (“Turbomill TA type” manufactured by Freund Turbo Co., Ltd.). The resulting finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.). Thus, a toner core A having a volume median diameter (D ₅₀ ) of 8 μm was obtained.

(Preparation of toner core B)
Toner core B was prepared in the same manner as toner core A except for the following changes. In the preparation of toner core B, 1,640 g (100 parts by mass) of the first binder resin (polyester resin 1) and magnetic powder ("Magnetite MRO-15A" manufactured by Toda Kogyo Co., Ltd., number average primary particles) were used as toner core materials. Diameter 0.18 μm) 1,600 g (97.6 parts by mass), carnauba wax (Kato Yoko Co., Ltd. “Special Carnauba No. 1”) 160 g (9.8 parts by mass), and an additive (N -71) 200 g (12.2 parts by mass) and 400 g (24.4 parts by mass) of inorganic particles (SW-350) as strontium titanate particles.

[Example 1]
(Preparation of shell layer material)
In an FM mixer ("FM-10C" manufactured by Nippon Coke Kogyo Co., Ltd.), 300 g of an additive (N-71) that is an azine compound, 600 g of inorganic particles that are strontium titanate particles (SW-350), and a second 600 g of a coloring resin (polyester resin 2) was added. The contents of the FM mixer were then mixed at a rotation speed of 2,000 rpm for 5 minutes. As a result, a shell layer mixture containing 100 parts by mass of the second binder resin, 50 parts by mass of the azine compound, and 100 parts by mass of strontium titanate particles was obtained.

The resulting shell layer mixture was extruded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) at a material feed rate of 6 kg/h, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 130 ° C. It was melt-kneaded under the following conditions. The resulting kneaded product was cooled. The cooled kneaded product was coarsely pulverized using a pulverizer ("Rotoplex (registered trademark) 16/8 type" manufactured by Hosokawa Micron Corporation) under the condition that the set particle diameter was 2 mm or less. Subsequently, the coarsely pulverized product of the kneaded product was crushed using a pulverizer ("Mill Stardam MSD-LB type" manufactured by Tokyo Atomizer Manufacturing Co., Ltd.) under the conditions of a tip peripheral speed of 100 m / sec and a processing amount of 7.2 kg / h. The mixture was pulverized to obtain a medium-pulverized kneaded product.

Next, a desktop sand mill (manufactured by Hayashi Shoten Co., Ltd.) equipped with a 2 L volume alumina ceramic container was prepared. 150 g of the medium pulverized product of the kneaded product, 15 g of an aqueous solution of an anionic surfactant (manufactured by Kao Corporation "Emar (registered trademark) 0", sodium lauryl sulfate) with a concentration of 10% by mass, and 335 g of distilled water are added to a tabletop sand mill. was put into a container of Subsequently, while maintaining the temperature of the container contents of the desktop sand mill at 50 ° C., using an ultrasonic cleaning device ("UT-106" manufactured by Sharp Corporation, high frequency output: maximum 100 W, oscillation frequency: 37 kHz), the contents of the container The object was subjected to ultrasonic irradiation for 5 minutes. As a result, the medium pulverized product of the kneaded material was sufficiently dispersed in the container of the desktop sand mill.

Next, 1,500 g of zirconia beads with a diameter of 1 mm were put into the container of the desktop sand mill. Then, pulverization was performed by rotating three discs made of alumina ceramic provided on a desktop sand mill. The pulverization conditions were a temperature of 53° C., a rotation speed of 2,160 rpm, and a processing time of 180 minutes. After that, 17.8 g of triethanolamine was added into the container of the desktop sand mill. Then, the pulverization treatment was performed again by rotating the three discs made of alumina ceramic provided on the desktop sand mill. The pulverization conditions were a temperature of 53° C., a rotation speed of 2,160 rpm, and a processing time of 60 minutes. After that, the zirconia beads were removed from the contents of the container of the desktop sand mill using a sieve with an opening diameter of 0.5 mm, and this was used as a shell layer material.

(Shell layer forming treatment)
After 500 g of the shell layer material (solid content: 144.8 g) and 400 mL of ion-exchanged water were put into a reaction vessel (2 L three-necked flask), toner core A (450 g) was further put thereinto. 1N Hydrochloric acid was added to the contents of the reaction vessel to adjust the pH to 4. The contents of the reaction vessel were then stirred for 1 hour at a rotation speed of 200 rpm. Then, the contents of the reaction vessel were heated to 70° C. at a heating rate of 1° C./min while being stirred at a rotational speed of 100 rpm. After the temperature was raised, the contents of the reaction vessel were stirred at a rotational speed of 100 rpm for 2 hours while maintaining the temperature at 70°C. Thus, a shell layer was formed on the surface of the toner core A. The contents of the reaction vessel were then adjusted to pH 7 by adding 1N aqueous sodium hydroxide solution. Next, the content of the reaction vessel was cooled to room temperature to obtain a toner base particle dispersion containing toner base particles. In the production of the toner of Example 1, the solid content of the shell layer material was 32.2 parts by mass with respect to 100 parts by mass of the toner core.

(washing treatment)
The obtained toner base particle dispersion liquid was subjected to suction filtration using a Buchner funnel. The resulting wet cake-like toner base particles were dispersed again in ion-exchanged water. The resulting dispersion was suction filtered using a Buchner funnel. Such solid-liquid separation treatment was repeated five times. As a result, wet cake-like toner base particles were obtained.

(drying process)
The resulting wet cake-like toner base particles were dispersed in an aqueous ethanol solution (concentration: 50% by mass). As a result, a slurry of toner base particles was obtained. The toner base particles in the slurry were dried using a continuous surface modification apparatus (“Coatmizer (registered trademark)” manufactured by Freund Corporation) under the conditions of a hot air temperature of 45° C. and a blower air volume of 2 m ³ /min. . Thus, powdery toner base particles were obtained.

(external addition processing)
Using an FM mixer (“FM-10C” manufactured by Nippon Coke Kogyo Co., Ltd.), 200 g (100 parts by mass) of toner base particles and dry silica particles (“AEROSIL (registered trademark) REA90” manufactured by Nippon Aerosil Co., Ltd., number average 2 g (1 part by mass) of primary particle diameter 20 nm) was mixed for 5 minutes. As a result, the external additive (dry silica particles) adhered to the surface of the toner base particles. The mixed powder was sieved using a 200-mesh (75 μm mesh) sieve. Thus, toner (T-1) of Example 1 was obtained.

[Examples 2 to 7 and Comparative Examples 1 to 7]
Toners (T-2) to (T-7) of Examples 2 to 7 and Comparative Examples 1 to 7 were prepared in the same manner as the toner (T-1) of Example 1, except that the following points were changed. ) and (t-1) to (t-7) were produced.

In the production of toners (T-2) to (T-7) and (t-2) to (t-7), the second binder resin, additive (azine compound or quaternary ammonium salt) and inorganic particles (strontium titanate particles or titanium oxide particles) and their amounts used were changed as shown in Table 1 below. In Table 1 below, "-" indicates that the corresponding component was not used.

In the production of toner (t-1) of Comparative Example 1, 200 g of toner core B was used instead of the toner base particles in the external addition treatment without performing the shell layer forming treatment. Toner (t-1) of Comparative Example 1 included toner core B (100 parts by mass) and an external additive (dry silica particles) adhering to the surface of toner core B (1 part by mass).

In the production of the toners (T-2), (T-3) and (T-5) of Examples 2, 3 and 5, in the preparation of the shell layer materials, the amounts of the materials put into the desktop sand mill were as follows. changed to street. First, the amount of medium pulverized kneaded product was changed to 300 g, the amount of anionic surfactant aqueous solution used was changed to 30 g, the amount of distilled water used was changed to 670 g, and the amount of zirconia beads used was changed to 2.5 g. 000 g, and the amount of triethanolamine used was changed to 26.7 g. Furthermore, in the production of toners (T-2), (T-3) and (T-5) of Examples 2, 3 and 5, the amount of shell layer material used in the shell layer forming process was 1,000 g ( solid content: 292.2 g). In the production of toners (T-2), (T-3) and (T-5) of Examples 2, 3 and 5, the mass of the solid content of the shell layer material relative to 100 parts by mass of the toner core was 64.9 mass. was the department. Table 2 below shows the solid content of the shell layer material and the amount of the toner core used in the production of each toner.

[cole-cole plot]
For the toners (T-1) to (T-7) and (t-1) to (t-7) of Examples 1 to 7 and Comparative Examples 1 to 7, the complex impedance was measured by the following method. Cole-cole plots created based on the measurement results are shown in FIGS. 3 to 5. FIG. 6 to 8 are enlarged views of the cole-cole plots of FIGS. 3 to 5 near the origin.

In the complex impedance measurement, samples (toner (T- ¹ ) to (T-7) and (t -1) to (t-7) any) 1 g was sandwiched. Then, a load of 40 kgf/cm ² was applied to the sample to shape the sample into pellets having a thickness of about 2 mm. A 1296 type dielectric interface (manufactured by Solartron) was connected to a frequency response analyzer (“1260 type frequency response analyzer (FRA)” manufactured by Solartron). The complex impedance was measured by connecting this frequency response analyzer to both ends of the electrodes.

The measurement conditions of the complex impedance were a voltage of 1 Vpp (effective voltage of 0.353 mV), a frequency of 1 MHz-10 mHz [5 pt/decade], and a measurement cycle of 3 cycles.

The measurement data of the complex impedance was taken in by controlling the measurement conditions via the measurement software "SMaRT (manufactured by Solartron)" from a personal computer. Using the analysis software “ZView2 (manufactured by Solartron)”, the captured data is fitted as an RC parallel circuit to obtain the resistivity ρ _H [Ωm], the dielectric constant ε _H [F / m] on the high frequency side, and its A time constant τ _H [sec] which is the product, a resistivity ρ _L [Ωm], a dielectric constant ε _L [F/m] on the low frequency side, and a time constant τ _L [sec] which is the product thereof were calculated. The calculation results are shown in Table 3 below. In Table 3 below, "-" indicates that the capacitive semicircle on the high frequency side and the capacitive semicircle on the low frequency side could not be distinguished.

<Evaluation>
The image density of each toner and the charge amount distribution of the toner chain formed on the developing roller were evaluated by the following methods. The evaluation was performed in a high temperature and high humidity environment (temperature 32.5°C, humidity 80% RH). The evaluation results are shown in Table 4 below.

A monochrome printer ("ECOSYS (registered trademark) FS-P3060DN" manufactured by Kyocera Document Solutions Co., Ltd.) was used as an evaluation machine. An object of evaluation (any of toners (T-1) to (T-7) and (t-1) to (t-7)) was put into the black developing device of the evaluation machine. In addition, toner (the same toner as the toner to be evaluated) was put into the black toner container of the multifunction machine.

Using the evaluation machine, a character original with a printing rate of 1% was printed on 5,000 sheets of printing paper in a double-sided mode. After that, an image for evaluation including a solid image was printed on a sheet of printing paper. Using a reflection densitometer (“TC-6D” manufactured by Tokyo Denshoku Co., Ltd.), the image density (ID) of the solid image on which the image for evaluation was printed was measured. An image density of 1.20 or more was evaluated as "good (A)", and an image density of less than 1.20 was evaluated as "bad (B)".

After that, the developing device was taken out from the evaluation machine. Using a Q/m meter ("MODEL 210HS-1" manufactured by Trek), the toner is sucked from the toner chain in the area corresponding to the development nip on the development roller of the development device, and the charge amount [μC/g] is measured. did. Specifically, first, a Q/m meter nozzle was arranged at a distance of 500 μm from the surface of the developing roller, and toner was sucked from the toner chain to measure the amount of suction and the amount of charge (first measurement). Next, after bringing the nozzle of the Q/m meter closer to the surface of the developing roller by 50 μm (distance from the surface of the developing roller: 450 μm), the toner was sucked from the toner chain and the amount of suction and the amount of charge were measured (measurement second time). In this way, the operation of bringing the nozzle of the Q/m meter closer to the surface of the developing roller by 50 μm and then sucking the toner from the toner chain and measuring the amount of suction and the amount of charge was performed by comparing the surface of the developing roller with the Q/m meter. This was repeated until the distance from the nozzle was 100 μm (9 measurements in total). This pulled all the toner in the toner chain by the Q/m meter.

Based on the above measurement results, the total charge amount of the toner in nine measurements was defined as the charge amount A [μC/g] in all layers of the toner chain. Also, the area of the toner chain up to 1 g/cm ² from the surface of the developing roller was regarded as the bottom layer of the toner chain. Then, the charge amount of the toner in the region corresponding to the bottom layer of the toner chain was calculated, and this was taken as the charge amount B [μC/g] of the bottom layer of the toner chain. Calculate the ratio (B/A) of the charge amount B [μC/g] in the bottom layer of the toner chain to the charge amount A [μC/g] in all layers of the toner chain. It was determined that the charge amount distribution of the toner chain applied was narrow. When the ratio (B/A) was 3.60 or less, it was evaluated as "good (A)", and when it was over 3.60, it was evaluated as "bad (B)".

Toners (T-1) through (T-7) of Examples 1-7 each comprised toner particles comprising toner base particles. The toner base particles had a toner core and a shell layer covering the surface of the toner core. The toner core contained a first binder resin and magnetic powder. The shell layer contained a second binder resin, an azine compound and strontium titanate particles. As shown in Table 4, each of the toners (T-1) to (T-7) of Examples 1 to 7 has a narrow charge amount distribution of the toner chain formed on the developing roller, and thus the image density was excellent.

On the other hand, the toners (t-1) to (t-7) of Comparative Examples 1 to 7 did not have the above structure. Specifically, the toner (t-1) of Comparative Example 1 did not have a shell layer, and instead had an azine compound and strontium titanate particles internally added to the toner core. In the toners (t-2) to (t-4) of Comparative Examples 2 to 4, at least one of the azine compound and the strontium titanate particles was not contained in the shell layer. In toner (t-5) of Comparative Example 5, a quaternary ammonium salt compound was added to the shell layer instead of the azine compound. In toners (t-6) to (t-7) of Comparative Examples 6 and 7, titanium oxide particles were added to the shell layer instead of strontium titanate particles. As a result, the toners (t-1) to (t-7) of Comparative Examples 1 to 7 were each poor in at least one of the charge amount distribution of the toner chain formed on the developing roller and the image density. rice field.

The toners of the present invention can be used, for example, to form images in copiers, printers, or multifunction devices.

1 Toner Particle 2 Toner Base Particle 2a Toner Core 2b Shell Layer 3 External Additive

Claims (6)

A toner comprising toner particles comprising toner base particles,
The toner base particles comprise a toner core and a shell layer covering the surface of the toner core,
The toner core contains a first binder resin and magnetic powder,
The toner, wherein the shell layer contains a second binder resin, an azine compound, and strontium titanate particles. 2. The toner according to claim 1, wherein the shell layer in the toner base particles has a mass of 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the toner core. 3. The toner according to claim 1, wherein the content of the azine compound in the shell layer is 15 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the second binder resin. The content of the strontium titanate particles in the shell layer according to any one of claims 1 to 3, which is 30 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the second binder resin. toner. The toner according to any one of claims 1 to 4, wherein the second binder resin contains a polyester resin. The toner according to any one of claims 1 to 5, wherein the strontium titanate particles have a number average primary particle size of 30 nm or more and 300 nm or less.

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